This book provides a complete overview of multi-hop relay systems with a focus on IEEE 802.16j. The authors have actively been participating in IEEE802.16j standardization since IEEE802.16j was established and Mike Heart is technical editor of IEEE802.16j. Divided into three parts, overview sections and sections on performance and comparisons with other technologies provide good context for a reader who is not familiar with relay and with 802.16j. Part 1 introduces the reader to the subject and will provide background information. It covers the basic background of broadband wireless and look at the motivation of multi-hop relay networks. The IEEE 802.16 standards are examined and the IEEE 802.16e architecture and technology are introduced. Part 2 focuses on IEEE 802.16j giving an overview of the key concepts and introducing the theories behind it. It covers the basics and frame structure through to security and performance with chapters also looking at path management, routing and scheduling and PHY support and enhancement. Part 3 looks at other related standards and technologies and explore the development and future of broadband wireless and multi-hop relay.